Just to give you another benchmark.
ASUS Rampage IV Formula
ASUS Strix GTX980Ti Direct CU III
i7 3930k 4.6 MHz
Windows 10 pro
Unigine Heaven
166,5 Frames
4193 score
I would say that you should get a much better benchmark result.
What MoBo do you use?
You know that the GeForce Serie 10xx has a different architecture than the other GeForce GPUs?
Wish you good luck to find the bottleneck.
Cheers
Spirit